Avaliação do dano bucal frente à exposição aguda e crônica ao herbicida ácido 2,4-diclorofenóxiacético (2,4-D)

Abstract

Introduction: The 2,4-dichlorophenoxyacetic acid (2,4-D) was the first selective herbicide produced and is widely used worldwide. Its characteristics (toxicity, persistence and bioaccumulation) make it harmful to human health. The mucosa of the oral cavity is one of the first areas that is contaminated by pesticides. Objective: To evaluate the possible effect on the oral mucosa of acute and chronic exposure to the 2,4-D herbicide. Material and methods: Acute phase: 80 male adult Swiss mice were divided into 4 groups (n = 20), evaluated at different time intervals (24h, 48h, 72h and 8 days), 5 animals/period: SG: nebulization with sodium chloride solution; LCG: pesticide nebulization with 3.71 x 10-3 grams of active ingredient per hectare (g.a.i./ha); MCG: pesticide nebulization at 6.19 x 10-3 g.a.i./ha; HCG: pesticide nebulization at 9.28 x 10-3 g.a.i./ha. Chronic phase: 80 adult male albino Wistar rats were divided into eight groups (n = 10): ICG - Inhaled Control Group, exposed to nebulization with distilled water; OCG - Oral Control Group, received nebulized ration with distilled water; ILCG Inhaled Low Concentration Group: exposed to nebulization to the herbicide at 3.71 x 10-3 g.a.i./ha; OLCG: Low Oral Concentration Group: received 3.71 x 10-3 g.a.i./ha nebulized feed with herbicide; IMCG: Inhalation Medium Concentration Group, exposed to nebulization to the herbicide at 6.19 x 10-3 g.a.i./ha; OMCG: Medium Oral Concentration Group, received nebulized ration with the herbicide with 6.19 x 10-3 g.a.i./ha; IHCG: Inhalation High Concentration Group, exposed to nebulization to 9.28 x 10-3 g.a.i./ha herbicide; OHCG: Group of High Oral Concentration, received nebulized ration with the herbicide with 9.28 x 10-3 g.a.i./ha. The animals of the chronic phase were euthanized 6 months after the beginning of the experiment. The tongue was collected for histopathological analysis. Results: There was a difference between exposure concentrations and tissue congestion intensity in acute (p = 0.002) and chronic (p = 0.000) exposure. Hyperkeratosis only occurred in chronically exposed animals orally. There was an increase in the number of nucleoli organizing regions (NORs) in dorsum in association with the concentration of 2,4-D in acute and chronic exposure (p < 0.001). The inhalation route was more associated with increased of mitotic figures and NORs. The oral route was more related to hyperkeratosis and intensity of tissue congestion. Conclusion: Acute and chronic exposure to high doses of 2,4-D caused an increase in congestion intensity, cell proliferation index, and tongue epithelium thickness and stimulated early inflammatory tissue response.